Optimise apt cache update task

The update of the apt cache and the package installation
can all be handled in a single task by providing the
package action plugin with the right parameters. This
removes an extra task to optimise execution.

The minimum Ansible version is raised to 2.2 due to a
known bug [1] in Ansible's apt module which does not
update the cache properly if the cache update and the
install are combined in a single task.

[1] https://github.com/ansible/ansible-modules-core/issues/1497

Change-Id: Ieaf67c9a776c43e9fd39c63a92642b55a49bb9bc
(cherry picked from commit 27545d222a)

meta/main.yml

@@ -4,7 +4,7 @@ galaxy_info:
   description: Deploy Trove with OpenStack Ansible
   company: OpenStack
   license: Apache-2.0
-  min_ansible_version: 2.0
+  min_ansible_version: 2.2
   version: 0.1.0
   platforms:
   - name: Ubuntu

tasks/trove_install.yml

@@ -16,17 +16,12 @@
 # (c) 2016 Donovan Francesco <donovan.francesco@is.co.za>
 # (c) 2016 Paul Stevens <paul.stevens@is.co.za>
 
-- name: Ensure apt cache is up to date
-  apt:
-    update_cache: yes
-    cache_valid_time: "{{ cache_timeout }}"
-  when:
-    - ansible_pkg_mgr == 'apt'
-
 - name: Install distro packages
   package:
     name: "{{ item }}"
     state: "{{ trove_package_state }}"
+    update_cache: "{{ (ansible_pkg_mgr == 'apt') | ternary('yes', omit) }}"
+    cache_valid_time: "{{ (ansible_pkg_mgr == 'apt') | ternary(cache_timeout, omit) }}"
   register: install_packages
   until: install_packages|success
   retries: 5